Not Applicable
Not Applicable
The present invention relates to a centrifuge for draining washed egg trays, comprising a centrifuge chamber in a housing, a bottom, means for holding the trays, and a drive for rotating the trays, said bottom and said housing being mutually displaceable between a feeding position in which the bottom is level with a feeding conveyor for wet egg trays, and a centrifuging position for egg trays enclosed in the centrifuge chamber of the housing.
The use of such centrifuges for draining egg trays are known from the U.S. Pat. Nos. 4,064,635 and 4,134,215. The egg trays are moved individually one after another through a washing station, and after washing, the individual egg tray is placed on a rotational drive part, and the drive part and egg tray are displaced vertically into the centrifuge chamber, and the single egg tray is centrifuged. After centrifuging the egg tray is moved to a stacking device. These centrifuges have to perform a full working cycle for each egg tray, and this consumes both time and energy. It is also a disadvantage that the egg tray is located at a maximum distance from the drive motor of the centrifuge when in the centrifuging position.
From U.S. Pat. No. 4,702,777 is known a dual-stack combined washing and centrifuging chamber, which is filled manually by an operator carrying stacks of trays over to the centrifuge and filling and emptying it. The prior-art centrifuge is designed as a separate unit in relation to the remainder of the washing line. Both the manual filling and the separation from the remainder of the production line result in extensive handling of the trays, which increases the risk of dirtying the trays just washed clean. In efficient washing lines the centrifuging may be a capacity-limiting part of the production line. The combination of washing and centrifuging into the same unit further limits the capacity of the unit. In this prior art combined washing and centrifuging unit the bottom is non-displaceable with respect to the housing, and the feeding and centrifuging positions are identical and the same as the washing position.
It is an object of the invention to provide an automatically functioning centrifuge of relatively high capacity for building in as an integral part of the production line.
This object is obtained by a centrifuge according to the invention characterized in that a stack of washed egg trays can be positioned on the bottom, that the stack of egg trays is centred on the bottom in the centrifuging position, and that, in said centrifuging position, the bottom is in engagement with said rotational drive which is vertically non-displaceable with respect to the housing.
Because the centrifuge is associated with a feeding conveyor and the bottom is at the same level as the bottom of the conveyed stacks, another stack can be fed mechanically and automatically onto the bottom of the centrifuge without the use of complex transfer mechanisms. This facilitates integration of the centrifuge in a production line and reduces the risk of erroneous positioning of stacks, which is of importance for achieving large capacity in the line. In view of operational reliability, it is an advantage that the bottom and the housing of the centrifuge have to be mutually moved after a wet stack of egg trays has been positioned and before centrifuging is initiated. During the mutual movement, the stack can be correctly adjusted in terms of centring and angular position in relation to the holding means and can be held in a suitable centrifuging position with the centre axis of the tray being substantially coaxial with the axis of rotation of the centrifuge.
In the feeding position, the centrifuge is in an open condition with access to sideways displacement of a stack of trays onto the bottom, and in the centrifuging position the centrifuge is in a closed condition, the housing enclosing the bottom and the stack. The mutual movement between bottom and housing may, for example, be made by moving the housing in relation to the bottom or by moving the bottom in relation to the housing. The movement between the two positions may suitably be a vertical displacement of the bottom and/or housing of the centrifuge, as the centrifuge may then have a substantially vertical axis of rotation. When the draining has been concluded, the centrifuge is opened by repeating the displacement carried out in connection with the closure in the opposite direction, and the stack is pushed out.
In the centrifuging position the bottom engages with a rotational drive for the bottom mounted so as to be vertically non-displaceable in relation to the housing. The vertical fixing of the drive gives the centrifuge a simple design, particularly if the bottom is vertically displaceable and, for example, made to engage with the drive at the end of the movement into the centrifuging position.
The means for holding the trays can rotationally fix the stack to the bottom during centrifuging, and suitably the means are movable in relation to the bottom BO that in the feeding position the means can be in a withdrawn position providing free passage for stacks of trays to and from the bottom.
In a preferred embodiment, elongated guides are mounted on a cover for upward closing of the centrifuge chamber, the ends of the guides opposite the cover having carriers for gripping and lifting the bottom, and in the centrifuging position the carriers are suitably located under the bottom with a clearance up to its lower surface. The movements of the cover and the bottom can thus be made by a single drive moving cover, guides and bottom in joint movements.
The centrifuge is suitable for building into a conveyor line so that it is located between the feeding conveyor and a discharge conveyor and so that at the feeding position a feeding opening faces sideways and is open towards the feeding conveyor, and a discharge opening faces sideways and is open towards the discharge conveyor.
Building in the centrifuge as an integral part of the system results in saving of the time otherwise to be spent on moving the stacks between the washing line itself and the centrifuge.
It is advantageous to feed a stack for accurate positioning on the bottom, thus minimising or avoiding subsequent adjustments of the stack position. In one embodiment, the still wet stack is pushed into the centrifuge by means of a pushing mechanism arranged in or in connection with the feeding conveyor, which mechanism suitably pushes the stack a well-defined distance that positions the stack in an end position which is centred in relation to the bottom.
To simplify the passage of stacks to and from the conveyors, the centrifuge preferably has a stop device that can stop the rotational movement of the bottom at one or more predetermined positions corresponding to a stack side surface facing in the discharge direction.
In an embodiment of the centrifuge the means for holding the trays comprise holders formed as upright rods located in the housing and fixed to a drive shaft in the rotational drive, and that in the centrifuging position the upright rods are located at each of the four corners of the stack. The upright rods at each corner of the stack provide secure holds on the stack along the complete height of the stack.
It is an advantage of the centrifuge that in the centrifuging position the stack can be closer to the drive motor of the rotational drive than in the feeding position because the drive will be subjected to less forces during centrifuging. This advantage is enhanced when displacement of the bottom in the height direction of the stack between the feeding and centrifuging positions is of considerable length in order to accommodate for high stacks.